Analyzing the effects of vertical acceleration and deceleration in multi-phase, debris-flow sediment-column experiments / by Christine Marie Williams.

Water-saturated debris flows are among some of the most destructive mass movements. Their complex nature presents a challenge for quantitative description and modeling. In order to improve understanding of the dynamics of these flows, it is important to seek a simplified dynamic system underlying their behavior. Models currently in use to describe the motion of debris flows employ depth-averaged equations of motion, typically assuming negligible effects from vertical acceleration. However, in many cases debris flows experience significant vertical acceleration as they move across irregular surfaces, and it has been proposed that friction associated with vertical forces and liquefaction merit inclusion in any comprehensive mechanical model. The intent of this work is to determine the effect of vertical acceleration through a series of laboratory experiments designed to simulate debris flows, testing a recent model for debris flows experimentally. In the experiments, a mass of water-saturated sediment is released suddenly from a holding container, and parameters including rate of collapse, pore-fluid pressure, and bed load are monitored. Experiments are simplified to axial geometry so that variables act solely in the vertical dimension. Steady state equations to infer motion of the moving sediment mass are not sufficient to model accurately the independent solid and fluid constituents in these experiments. The model developed in this work more accurately predicts the bed-normal stress of a saturated sediment mass in motion and illustrates the importance of acceleration and deceleration.

The 1452 or 1453 A.D. Kuwae Eruption Signal Derived from Multiple Ice Core Records: Greatest Volcanic Sulfate Event of the Past 700 Years

We combined 33 ice core records, 13 from the Northern Hemisphere and 20 from the Southern Hemisphere, to determine the timing and magnitude of the great Kuwae eruption in the mid-15th century. We extracted volcanic deposition signals by applying a high-pass loess filter to the time series and examining peaks that exceed twice the 31 year running median absolute deviation. By accounting for the dating uncertainties associated with each record, these ice core records together reveal a large volcanogenic acid deposition event during 1453 - 1457 A. D. The results suggest only one major stratospheric injection from the Kuwae eruption and confirm previous findings that the Kuwae eruption took place in late 1452 or early 1453, which may serve as a reference to evaluate and improve the dating of ice core records. The average total sulfate deposition from the Kuwae eruption was 93 kg SO4/km(2) in Antarctica and 25 kg SO4/km(2) in Greenland. The deposition in Greenland was probably underestimated since it was the average value of only two northern Greenland sites with very low accumulation rates. After taking the spatial variation into consideration, the average Kuwae deposition in Greenland was estimated to be 45 kg SO4/km(2). By applying the same technique to the other major eruptions of the past 700 years our result suggests that the Kuwae eruption was the largest stratospheric sulfate event of that period, probably surpassing the total sulfate deposition of the Tambora eruption of 1815, which produced 59 kg SO4/km(2) in Antarctica and 50 kg SO4/km(2) in Greenland.

Horizontal profiles of longwave and shortwave radiation components over sea ice near Barrow, Alaska during the 2011 melt

An integrated instrument package for measuring and understanding the surface radiation budget of sea ice is presented, along with results from its first deployment. The setup simultaneously measures broadband fluxes of upwelling and downwelling terrestrial and solar radiation (four components separately), spectral fluxes of incident and reflected solar radiation, and supporting data such as air temperature and humidity, surface temperature, and location (GPS), in addition to photographing the sky and observed surface during each measurement. The instruments are mounted on a small sled, allowing measurements of the radiation budget to be made at many locations in the study area to see the effect of small-scale surface processes on the large-scale radiation budget. Such observations have many applications, from calibration and validation of remote sensing products to improving our understanding of surface processes that affect atmosphere-snow-ice interactions and drive feedbacks, ultimately leading to the potential to improve climate modelling of ice-covered regions of the ocean. The photographs, spectral data, and other observations allow for improved analysis of the broadband data. An example of this is shown by using the observations made during a partly cloudy day, which show erratic variations due to passing clouds, and creating a careful estimate of what the radiation budget along the observed line would have been under uniform sky conditions, clear or overcast. Other data from the setup's first deployment, in June 2011 on fast ice near Point Barrow, Alaska, are also shown; these illustrate the rapid changes of the radiation budget during a cold period that led to refreezing and new snow well into the melt season.

Troya historiada en The Book of the Duchess y The House of Fame

En este trabajo propongo analizar The Book of the Duchess y The House of Fame a partir de los problemas que introduce la presencia de la historia troyana. El famoso relato está invocado a través de escenas pintadas en paredes o en ventanales, presentados como escenografía. No están incluidos para añadirles nuevas interpretaciones, ni para completar faltantes de información o conciliar versiones divergentes, sino que son utilizados para capitalizar sus resonancias como objeto cultural, incorporado a la memoria social, frente al cual Chaucer construye un universo de sentido para su propia poesía e indaga en los principios que autorizan su texto.

Troya historiada en The Book of the Duchess y The House of Fame

En este trabajo propongo analizar The Book of the Duchess y The House of Fame a partir de los problemas que introduce la presencia de la historia troyana. El famoso relato está invocado a través de escenas pintadas en paredes o en ventanales, presentados como escenografía. No están incluidos para añadirles nuevas interpretaciones, ni para completar faltantes de información o conciliar versiones divergentes, sino que son utilizados para capitalizar sus resonancias como objeto cultural, incorporado a la memoria social, frente al cual Chaucer construye un universo de sentido para su propia poesía e indaga en los principios que autorizan su texto.

Troya historiada en The Book of the Duchess y The House of Fame

En este trabajo propongo analizar The Book of the Duchess y The House of Fame a partir de los problemas que introduce la presencia de la historia troyana. El famoso relato está invocado a través de escenas pintadas en paredes o en ventanales, presentados como escenografía. No están incluidos para añadirles nuevas interpretaciones, ni para completar faltantes de información o conciliar versiones divergentes, sino que son utilizados para capitalizar sus resonancias como objeto cultural, incorporado a la memoria social, frente al cual Chaucer construye un universo de sentido para su propia poesía e indaga en los principios que autorizan su texto.